Source

File: wp-includes/class-wp-http-encoding.php

public static function decompress( $compressed, $length = null ) {

		if ( empty( $compressed ) ) {
			return $compressed;
		}

		$decompressed = @gzinflate( $compressed );
		if ( false !== $decompressed ) {
			return $decompressed;
		}

		$decompressed = self::compatible_gzinflate( $compressed );
		if ( false !== $decompressed ) {
			return $decompressed;
		}

		$decompressed = @gzuncompress( $compressed );
		if ( false !== $decompressed ) {
			return $decompressed;
		}

		if ( function_exists( 'gzdecode' ) ) {
			$decompressed = @gzdecode( $compressed );

			if ( false !== $decompressed ) {
				return $decompressed;
			}
		}

		return $compressed;
	}